A conventional image forming device has a photosensitive drum and a developing device. The developing device includes a developing unit and a toner box. The developing unit has a casing on which the toner box accommodating toner is mounted.
The toner box is formed in a shape having a circular circumferential surface, for example. The circular circumferential surface is formed with a toner discharge port for discharging toner toward an interior of the casing. The toner discharge port has a peripheral area provided with a seal member for preventing toner leakage. Further, a shutter is slidably movably provided at an outer periphery of the circular circumferential surface to open and close the toner discharge port.
After the toner box is mounted on the casing of the developing unit, the shutter is slidingly moved to open the toner discharged port. As a result, a toner supply passage is defined between the toner box and the casing through the toner discharge port. Toner is supplied to the casing from the toner box via the toner supply passage.
When an image is formed, an electrostatic latent image is formed on a surface of the photosensitive drum, and a toner image is formed on the photosensitive drum based on the electrostatic latent image. While forming the image, toner is consumed. When toner accommodated in the toner box runs out, the toner box is removed from the casing. Then, a new toner box is mounted on the casing.
Before removal of the toner box from the casing, the shutter is slidingly moved to a position confronting the toner discharge port to close the toner discharge port. In this state, the shutter is compressed by the seal member, thereby sealing any gaps formed between the shutter and the peripheral area of the toner discharge port. Therefore, while the toner box has been removed from the casing, leakage of toner remaining in the toner box from the toner discharge port can be avoided.